Voltage pulse generator



NGV. 28, A R SIMPSON VOLTAGE PULSE GENERATQR Filed Aug. 16, 1944INVENTOR. Z/W jzpfon/ VBY Patented Nov. 28, 1950 VOLTAGE PULSE GENERATORAlbert R. Simpson, Knoxville, Tenn., assignor to the United States ofAmerica as represented by the United States Atomic Energy CommissionApplication August 16, 1944, Serial No. 549,737

(Cl. Z50-36) 3 Claims.

This invention relates to circuit arrangements for producing pulses ofelectrical energy and has for its principal object the provision of animproved source of periodic short sharp voltage pulses of knownfrequency and intensity.

It is frequently desirable to have available such a source of voltagepulses which is especially useful in the testing and Calibrating ofcounter circuits where it is desirable to simulate the Waveshape andfrequency of pulses produced by ionization chambers, G-M counters andthe like.

The present invention provides a means for furnishing short sharp pulsesthe frequency and intensity of which may be varied over wide ranges andthe polarity of which may be selected.

In the practice of the invention the discharge time of a relaxationoscillator determines the duration of the pulse while the charging timedetermines the interval between pulses, i. e., the frequency. In thepreferred embodiment of the invention, this is accomplished byemployingl a thyratron tube in the relaxation circuit and connecting itscontrol electrode to the control grid of a suitable amplifier tube sothat Whenever the thyratron is conducting, a signal voltage is impressedon the grid of the amplifier tube.

My invention will be better understood from the following descriptionwhen read in connection with the accompanying drawing, and its scopewill be pointed out in the appended claims.

In the drawing, the single figure shows a circuit network supplied withdirect current by a suitable source I` which for simplicity is hereshown as a battery. Current owing through a resistance II furnishes avoltage for charging a condenser I2 through resistances I3 and I4. Athyratron tube I5 in series with a resistance I6 provides a dischargepath for the condenser I2 when it has charged to the critical potential.It will be appreciated that the circuit thus far described constitutes arelaxation oscillator the frequency of which may be set for diierentranges by selecting different condensers I2a, I2b, or I2c by means of aselector switch I'I and which ranges can be varied by adjustingresistance I4. When the thyratron I5 discharges the condenser I2, itscontrol electrode I8 goes positive to provide a short sharp signal whichis amplified by tubes I9 and 2D and made available for use at outputleads 2| and 2Ia. The grid of tube I9 is normally at ground potentialand is connected through a limiting resistance 22 and a couplingresistance 23 to receive the positive voltage pulses of the controlelectrode I8 Whenever the thyratron I5 conducts.

l A resistance 24 between the anode of the tube I9 and the source IIIand a resistance 25 between its cathode and ground are so selected thatwhen no signal is impressed on its grid it will pass a current suicientto provide a desired voltage drop across the resistance 25 therebymakingits grid negative with respect to its cathode. The second amplifier tube2I| has its anode connected to the source I Il through a resistance 26,its cathode connected to ground through a resistance 2l and its gridconnected to its cathode through a resistance 28. The resistances 26 and21 are preferably equal and so chosen as to have voltage dropscorresponding to the magnitude of the signal desired at the output 2 I.A convenient value for these voltage dro-ps has been found to be ftyvolts.

The operation of the circuit will be readily understood if it is assumedthat the condenser I2 is receiving a charge. This charge and thereforethe voltage on the anode of the thyratron I5 will increase at a ratedetermined by the time constant of the condenser I2 and the resistancesI3 and I4 circuit until the thyratron I'5 fires to discharge thecondenser I2. The momentary current surge through the thyratron I5creates on its control electrode I'B a positive voltage corresponding inintensity and duration to the current surge. This positive voltage pulsedrives the grid of the tube I9 positive to give a corresponding increasein its plate current. This increase in plate current through the tube I9decreases the voltage on its plate and this sudden decrease in voltageis transferred through a coupling condenser 29 to the grid of the secondamplifier tube 20 to drive its negative and practically cut off thecurrent now between its plate and cathode, whereby the voltage drops(fifty volts) across the resistances 2B and 21 appear as voltage pulsesin their respective output terminals 2l and 2m. I'hese output voltagepulses Will have the same general wave shape as the discharge currentthrough the thyratron I5.

It will be evident that when the amplifier tube 20 suddenly becomesnonconducting a positive voltage will appear on terminal 2| and anegative voltage pulse will appear on terminal 21a. By means of a switch3U either of these voltage pulses may be selectively applied through acondenser 3I to a counter circuit 32 which itis desired to test orcalibrate.

Although adjustment of the coupling resistance 23 will change theintensity or height of the voltage pulses appearing on the outputterminals 2| and 2 la, it has been found convenient to have a means foradjusting the strength of these pulses in known steps and for thispurpose a movable Contact arm 33 is arranged for selectively connectingthe counter circuit 32 to a condenser 34 and a group of resistances 35,3B, 31, and 38 which preferably are so proportioned as to attenuate thesignal in equal steps and thereby make it possible to check theoperation or response of the counter circuit 32 to signals differing aknown amount in intensity.

In order that the delivery of signal pulses to the output 2| may beinterrupted Without necessitating the deenergization of the severaltubes a switch 39 is provided for grounding the signal prior to itsbeing impressed on the grid of the second amplifier tube 2U.

Although a preferred embodiment lof the invention has been illustratedand described to make clear the novel features thereof, it will beobvious to those skilled in the art that the invention may take modifiedforms to meet various conditions Which may be encountered in differentspecific uses, and it is therefore intended to cover by the appendedclaims all such modifications which fall within the spirit and scope ofthe invention.

I claim:

1. An oscillation generating circuit comprising a gas dischargethyratron tube having a cathode, control grid, and anode electrodes; asource of potential exceeding the value required to ionize the gasbetween said anode and cathode, resistance means and capacitance meansconnected in series relationship, said capacitance means being connectedin parallel relationship with the discharge path through said tube; andoutput circuit means for extracting pulses of energy from said tubecomprising said control grid and a conductor connected thereto.

2. A pulse generating circuit comprising resistance means, capacitancemeans, a source of electrical potential connected thereto through saidresistance means for charging said capacitance means, a gas-dischargetube having a cathode, anode, and control grid, said tube beingconnected to furnish a discharge path for said capacitance means; and anoutput circuit including said control grid, means for maintaining saidcontrol grid at a relatively` fixed potential `While said tube is notconducting, and conductive means connected to said control grid forextracting energy therefrom when said tube is rendered conductive.

3. 1n combination, a gas discharge tube having cathode, grid, and anodeelectrodes; capacitance means, resistance means, and a source ofelectrical potential connected inthe anode-cathode circuit of said tubeto form a relaxation oscillator; and' means for extracting energy fromsaid tube comprising `said grid electrode and a conductor connectedthereto.

ALBERT R. SIMPSON.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Y Date 2,027,054 Miessner Jan. 7, 19362,092,861 Swart Sept. 14, 1937 2,118,626 Smith May 24, 1938 2,144,779Schlesinger Jan. 24, 1939 2,163,214 SchlesingerV June 20, 1939'2,170,252 Schlesinger Aug. 22, 1939 2,179,414 Konkle Nov. 7, 19392,202,055 Burnett May 7, 1940 2,227,021 Schlesinger Dec. 31, 19402,495,095 Murnma July 30, 1946

